Invited Papers

Direct manipulation interfaces, where objects on the screen can be pointed
to and manipulated using a mouse and keyboard, are now almost universally
accepted. However, some limitations of these interfaces are well known. These
include the lack of programmability and the difficulty of providing abstract
commands. Demonstrational interfaces can overcome these problems while still
providing the benefits of direct manipulation. A "demonstrational interface"
watches while the user executes conventional direct manipulation actions, but
creates a more general abstraction from the specific example. For instance,
the user might drag a file named v1.ps to the trash can, and then a file named
v2.ps, and a demonstrational system might automatically create a macro to
delete all files that end in .ps. This paper defines demonstrational
interfaces, presents a number of examples, and then discusses some potential
application areas.

The importance of a user-centred approach to multimedia interface design is
stressed. We must respond to what users wish to do rather than considering
what users might be able to do. Much existing multimedia research has been
disappointing partly because of a concentration on exploratory presentation
approaches rather than on investigations of how media in combination can
improve human-computer bandwidth. Multimedia terminology is examined and
suggestions are made as to how to improve the terminology. Arguments are put
forward to support more research into multimedia devices and for
knowledge-based support for non-deterministic multimedia situations. Finally a
set of questions is posed as a possible research agenda.

HCI Frameworks

The contextualist critique of HCI theories and frameworks both complicates
the analyst's job and enriches the analytical result by permitting, indeed
requiring reference to situational details of user interaction. It is
suggested that this critique be broadened to envision HCI as fundamentally
historical, relativizing situational details to points in time, and taking
remote direct causation (hysteresis) as the usual state of affairs. This
further enrichment may have the same double-edged effect on analysis in the
field.

This paper reviews current Software Engineering practice and User Interface
Management research on internal software structure. It argues that existing
analytical categories in Software Engineering do not expose the structural
properties emphasised by recent developments in User Interface Management. New
analytical categories are introduced, and it is shown that there are direct
connections between these categories and important HCI goals such as
flexibility, consistency and task fit. HCI goals are thus relevant to the
internal structure of software, and not just to the inputs, methods and
techniques of the design and testing stages of software development
methodologies.

We introduce a basic framework for the analysis of existing interactive
systems which will also serve for the principled design of more usable systems.
We present a simple yet effective model of an interactive system that extends
previous interaction frameworks. Within our framework, the user, system and
interface are all represented equally. We also present several notions of
distance as qualitative measurements of the interactive features of a system
based on specific tasks. These notions of distance can be formalised to give
an understandable quantitative approach required for principled design and
analysis.

Keywords: Framework, Analysis and design, Formal methods

Scenarios and Rationales in Design

Signature Tasks and Paradigm Tasks: New Wrinkles on the Scenarios
Methodology

Scenarios are increasingly being used in HCI to explore alternative designs
or assess user models. We seek to strengthen the use of scenarios within
modelling methodologies by clarifying what scenarios are good for and what
makes a good scenario. The first clarification concerns scenarios that are
"privileged" in certain ways with respect to the modelling technique used to
analyse them. A signature task is one deliberately chosen to match the
capabilities of the technique. A paradigm task is one which has been
thoroughly analysed and understood in terms of the technique. Perhaps
surprisingly, signature tasks and paradigm tasks are often not the same. The
second clarification is that although scenarios represent a particular concrete
instance of human-computer interaction, some form of contrast is generally
involved -- whether explicitly stated or merely implied. Good scenarios are
characterised by the presence of a meaningful contrast that captures an issue
and focuses the analysis.

There are many factors which drive software design. This paper focuses on
the use of scenarios by designers and examines the effect this has on the
design process. Scenarios are examples of user interactions with systems which
are used to structure and communicate information about how a design might be
used in the real world. The use of scenarios was examined in a study of
designers in a commercial setting engaged in the design of an air traffic
control system. The findings are used to make recommendations about how design
should be done and also about the tools required to support design.

This paper discusses the preliminary results and ongoing work of a
collaborative research project which investigates methods to communicate the
Human-Computer Interaction expertise of a human factors consulting group in a
large corporate setting. The objective of the project is to extend the
contribution of the human factors group. Their existing direct consultation on
user-interface design will be combined with new methods which allow the results
of those consultations to be widely accessible. The current experiments focus
on design rationales and scenarios for user interfaces as the methods for
communicating the expertise.
In work to date, we have adapted previous research on design rationales for
our new context of use. This has produced an enhanced format for recording and
presenting design decisions and the reasoning process behind them. We have
produced a prototype presentation system, seeded with design rationales from a
large project with extensive involvement by the human factors group. This
prototype is currently undergoing iterative test and refinement.
We have also developed a framework for access to this information, by
product engineers working on user interfaces, using complementary tables of
contents within a hypertext space. These paradigms, or ways of looking at a
user interface design problem, are themselves an important component of HCI
expertise.

Groupware

The classical perspective in the study of human-computer interaction has
focussed upon single users operating single systems. Interactive dialogues in
such applications are often assumed to be sequential and deterministic. These
assumptions support operator predictions about the effects of their commands.
Unfortunately, there are an increasing number of applications for which such
assumptions are no longer appropriate. This paper examines approaches which
support predictability in systems, such as groupware and process control, where
execution may be neither sequential nor deterministic.

Keywords: Predictability, Process control, Groupware

Applying Temporal Logic to Support the Specification and Prototyping of
Concurrent Multi-User Interfaces

First order logic provides a concise and precise means of specifying
interface requirements for complex systems. Designs can be constructed in
terms of high level abstractions which avoid the representation of unstructured
bitmaps and 'raw' devices during the early stages of the development process.
Unfortunately, logic specifications provide the non-formalist with little idea
of what it would be like to interact with potential implementations. This
limitation can be avoided by employing executable subsets of first order logic
to rapidly derive prototypes from high level specifications of interactive
systems. The following pages show how this formalism must be extended in order
to support the design of concurrent multi-user systems, such as joint-editors,
conferencing or distributed control applications. The introduction of a
temporal ordering into logic specifications provides a means of analysing
concurrency and contention between multiple users of shared resources. PRELOG,
a tool for Presenting and REndering LOGic specifications has been enhanced to
support this investigation.

This paper presents current work on software to support collaborative
workstation design. Prevailing problems with groupware systems which prevent
their widespread use for software engineering tasks such as systems design,
software engineering, and computer-aided design are discussed and the methods
for alleviating these problems through the use of collaborative workstation
design are described. The collaborative workstation design model introduces
strategies for dealing with synchronous work problems such as data and view
integrity, view coordination, and change arbitration as well as asynchronous
work problems such as version control and presentation of design modifications.

Keywords: Computer supported cooperative work, Groupware

Graphical Interaction

Iconographer, a tool for exploring alternative iconic representations of
objects, is briefly introduced. Its own user interface, which itself is
largely though not completely visual (pictorial), is described in detail: it
comprises five separate interactive representations. These visualisations are
then analysed in an attempt to understand their nature and limitations. This
analysis is then supported by showing how Iconographer can be directly extended
to an isomorphic, yet apparently quite different, task: a subset of the class
of data processing programs addressed by the JSD (Jackson System Development)
method.

Iconographer is a toolkit that allows designers to explore alternative
iconic representations of collections of application entities in a highly
interactive manner. This paper describes the development of a complementary
facility for exploring alternative regimes for interacting with these generated
iconic representations. This mechanism provides a flexible means for selecting
and modifying entities and their attributes' values using a strict direct
manipulation style of interaction. The paper considers generalised editors and
virtual input devices as a means of implementing this input mechanism.

All current paint systems are based on the same conceptual model. This
model does not actually model real paint as an artist would understand it,
rather it is more akin to a potato-cut printing technique. This paper
describes an interactive model of real paint, "Wet and Sticky", and its
successor, "Wet and Runny". Both models provide the artist with a realistic,
simulation of real, wet paint applied to a canvas.

Keywords: Paint modelling and systems, Novel interaction, Parallelism

Evaluation

This study examines the focus group as an evaluation technique. Many of the
methods used for user requirements capture and for evaluation of usability
suffer from being individual based. This leads to serious concerns over the
validity of techniques. It is noticeable that in the plethora of definitions
of usability and in the variety of techniques (both 'objective' and subjective)
pressed on the designer for employment during user requirements capture,
prototype evaluation and field evaluation, the issues of reliability and
validity are not often in focus.
This paper addresses the question of construct validity as it affects
specifically the focus group in HCI. A central heating control interface from
Honeywell Control Systems was subjected to prototyped based evaluation using a
range of different techniques including a focus group. 20 subjects operated a
predesignated task scenario on an interface and had their performance
videotaped. Indexes of performance were calculated, time for sub task
completion and error rate. Subjective assessments by subjects of the
performance were also taken as were a range of other measures. Subjects then
took part in a moderated focus group. The discussion was content analysed and
measures of satisfaction/dissatisfaction constructed.
Measures derived from the task scenario were correlated with the focus group
based measures. The scenario based measures predicted the focus group indexes
especially the number of criticisms uttered. However some dimensions of
subject evaluation were not predicted by the scenario measures. This implies
that the construct validity of the focus group does not overlap completely with
that of other evaluation techniques.

In this paper, we report on a case study to evaluate the introduction,
organization and planning of education utilizing new technology in order to
obtain an understanding of the different needs for users and enterprises in
multimedia learning environments. Two different interactive video training
packages were tested in this study. Evaluation methods comprised a combination
of seminars, questionnaires, video recordings and interviews. In total 125
users participated in the study. The results show that: a mouse-based
interaction technique and a 'point-and-click' dialogue certainly simplify the
users' interaction with a system, but they also make it easier for users to
make mistakes. If implemented as a point-and-click dialogue, direct
manipulation tends to become semantically overloaded confusing the users'
interaction with the system. A major drawback of the system tested was its
insufficient support for navigation and browsing. The mere possibility of
obtaining feedback from a system and not from another person was highly
appreciated by the users and positively influenced their willingness to try
different parts of the system. Finally we discuss the design of a
learner-driven system that provide both a teacher-directed and a
learner-directed interaction.

An experimental study investigated three distinct components of usability,
that account for how a user's performance with a system changes with learning:
guessability, learnability, and experienced user performance (EUP). Two small
experiments, involving the performance of simple editing tasks on a word
processor, were used to illustrate these components. Further possible
components of usability are discussed with a view to obtaining a comprehensive
definition.

UIMS and Workstations

This paper presents a precise but general architecture (UMA) which attempts
to resolve two critical but conflicting qualities of graphical user interfaces:
directness and separation. This is achieved by placing central emphasis on the
medium of interaction, and making this active through a dedicated user agent.
The active medium allows surface interaction -- application-independent
manipulation of medium objects by the user. A major strength of UMA is that it
is both a conceptual and an implementation architecture, and therefore is both
intuitive to the user and the application designer, and effective in
rationalising the separate construction and execution of the user interface and
the application.

This paper describes the work done in developing the visual style for a BT X
Windows system graphical user interface toolkit. The approach to this design
was innovative because it involved a team which had training in both graphical
information and industrial design, in addition to more conventional human
factors/HCI experience. This had a considerable impact on working methods,
several of which were drawn from traditional design practice. The two
principle design aims were to improve usability and convey an appropriate
product identity and corporate image. These were achieved by appropriate and
consistent representation and rendering of interactors in a range of states.

This paper explores the techniques necessary to build a domain specific
predictive reference model which can be used to improve the performance of a
speech recognition interface to a word processor. It draws on the expertise of
Speech and Language Technology Group members in task analysis, linguistic
analysis and data structure design. The results of initial evaluations and
analysis are presented and the implications for the model design are discussed.

Cognitive Dimensions

(Green, 1989) coined 'cognitive dimensions' to describe the cognitively
important aspects of an information artifact for a given style of interaction,
such as exploratory design, and to show how computer environments could provide
tools tailored to complement notations. Cognitive dimensions provide a useful
and much-needed vocabulary for discussing designs, but the problem is to define
them clearly. This paper introduces 'structure maps' in which the information
dependencies of many diverse notations and artifacts can be analysed in ER
terms, and unexpected similarities can be brought to light. Structure maps go
some way to defining certain of the cognitive dimensions: other dimensions
still need to be defined by reference to psychological models.

This paper presents an analysis of visibility -- a common HCI guideline
which is often only loosely described. Although it might appear that
visibility should be thought of as a cognitive dimension of notations (Green,
1989), my analysis separates it into three dimensions, two of which are static
properties of the notation, while the third is dynamic. The two static
dimensions are accessibility and salience, both of which can be examined
through the use of structure maps (Green, 1991), whilst the third dimension is
congruence which changes according to the user, their task and their strategy.
Accessibility refers to the ease with which information structures can be
accessed (psychologically), and this is assessed directly from the structure
map and the number of different routes to certain information. Salience refers
to the relative accessibility of an information structure in a display --
relative to the accessibility of other information structures in the display.
Congruence reflects the extent to which the salient structure is relevant to
the use being made of the display at any moment.
An information search task is used to provide experimental evidence for this
analysis, revealing that the effects of accessibility and salience on search
performance and search strategy are separable. Accessibility affects speed of
performance, but not strategy, whereas salience has an effect on strategy
choice, and not necessarily on speed. The results also suggest that it is
important to consider a display congruence, which is the match between the
information structure required by the users strategy and the salience of that
structure.
The paper concludes with a brief analysis of the visibility of various
programming languages, revealing that the dimensions of visibility can be
assessed.

A design rationale (DR) is a representation of the reasoning behind the
design of a system. One of the primary goals in developing a usable DR
environment is minimising the cognitive overhead of representing design
deliberation in a structured form. This paper examines some of the cognitive
attributes of various DR notations, focussing on how generic cognitive
dimensions of notations can be operationalised to clarify the relationship
between DR notations and the DR authoring process. It is shown how cognitive
dimensions analysis makes explicit some of the requirements for DR authoring
environments, highlighting the importance of supporting intermediate DR
representations; these 'rough DRs' evolve as design reasoning unfolds, to
reflect new perspectives on the design space.

Applications

A software development project was undertaken to show how modern User
Interfacing Techniques could significantly improve the usability of an existing
Police System. The following reports the User-Centred approach taken to this
work, including difficulties encountered. A formal evaluation was undertaken
of the work. This is reported at some length as an example of the difficulties
of performing usability evaluations within viable timescales.

This paper examines the potential benefits of conversational
computer-mediated communication aids for the speech and hearing impaired. The
importance of turn-taking protocols for effective conversation management is
discussed. Results are presented of a preliminary study of turn-taking
behaviour in a text-based conversational aid, and the effectiveness of an
explicit turn-taking signalling mechanism is assessed.

The increasing reliance on visual forms of communication in modern computer
interfaces poses severe problems for blind users. A possible solution is to
make greater use of auditory communication. Speech has obvious applications,
but is slow and hence not useful in situations where immediate feedback to the
user is essential, such as when locating items using a mouse. Experiments have
been carried out in order to ascertain the best way in which to use non-speech
sounds to guide the user in locating such targets. The guiding principle has
been to modulate the sounds in a manner which is as natural as possible, so
that people can exploit their every-day listening skills. Some success has
been achieved, particularly through the use of stereo sounds to give
two-dimensional spatial sound guidance.

Task Analysis

User models as psychological models useful to HCI practitioners and system
designers are discussed and a form of designer's user model based on logical,
as opposed to psychological, behaviourism is proposed. A small survey of
recently published work on user models suggests that many models have a weak
empirical basis.

This paper reports a feasibility study to investigate the possible use of
the programming language PML (Process Modelling Language) for task analysis.
In so doing, it proposes a number of criteria for assessing task analyses. The
study used PML to analyse and describe the task of producing a multi-author
research proposal. To assess the suitability of PML for this purpose, a number
of criteria were identified, concerning the effectiveness of: the task analysis
product; the task analysis method notational support; and the task analysis
method procedural support. The assessment of PML suggests that it may well be
suitable for task analysis, generating a task analysis product particularly
appropriate for software engineers developing multi-role systems, and offering
a clear notation for a task analysis method. Its principal weakness is the
lack of procedural support it provides as a task analysis method.

Keywords: Task analysis, Process modelling, Multi-user systems

Space and Location

Cognitive Representations of Space in the Design and Use of Geographical
Information Systems

Geographical Information Systems (GIS) are multi-user, multi-functional
systems concerned with handling and analysing spatially-referenced data. While
technically sophisticated they are still poor with regard to their degree of
usability. Although ergonomic principles can be applied to improve the
usability of such systems, a more effective approach is to reduce the amount of
cognitive and behavioural modification required by the user by incorporating
ideas of how they represent and think about space into the design of GIS.
The purpose of this paper is to summarize some of the research currently
being conducted into GIS design using this cognitive-behaviourist approach
(i.e. user interfaces, spatial query languages, visual representations,
conceptual design). The paper begins by describing our current knowledge about
how people mentally represent and transform space and then describes how this
knowledge is being and might be applied to the design of more usable GIS.